注二氧化碳和氮气提高煤层气采收率的经济评价及敏感性分析

Economic Evaluation and Sensitivity Analysis of Enhanced Coalbed Methane Production with CO_2 and N_2 Injection

应用耦合的煤层气数值模型,模拟和对比了不同注入气体和煤基质力学参数对开采方案的影响。在氮气购买价格分别为二氧化碳购买价格的1倍、2倍、3倍和4倍的情况下,最好的提高采收率方案分别为注纯氮气、75%N2+25%CO2的混合气、50%N2+50%CO2的混合气、25%N2+75%CO2的混合气,当超过4倍时,注纯二氧化碳的方案最好;结果表明注入气体的组份、气体价格和煤基质的力学参数对开发方案的可行性、收益大小和开采年限具有较大的影响。

The influence of injection of different gases, gas price and mechanical parameters of coal matrix on methane output and the mining scheme is simulated and compared by using a coupled CBM numerical model. With the decrease of mole percentage of nitrogen in the injected gas, the cumulative output of methane reduces successively. Under the conditions when the purchase price of nitrogen being one, or two, or three, or four times of that of carbon dioxide respectively, the best proposals for improvement of recovery rate are as the following： gas mixture with pure nitrogen, gas mixture with 75%N2 ＋ 25%CO2, mixture with 50%N2 ＋ 50% CO2, and 25 % N2 ＋ 75 % CO2. When the price of nitrogen is four times higher than carbon dioxide, the best proposal is to inject pure carbon dioxide. The results indicate that the compositions and price of gas and the mechanical parameters of coal matrix have a great influence on feasibility of development scheme, the magnitude of profit and working life.